Process for the chemical treatment of textile goods

ABSTRACT

A PROCESS FOR THE CHEMICAL TREATMENT OF TEXTILE GOODS, E.G. THE DYEING, DRESSING OR FINISHING OF TEXTILE FIBERS, YARN, THREAD OR FABRIC, WHEREIN THE CHEMICAL-TREATMENT AGENT IS SLIGHTLY SOLUBLE IN AN ORGANIC SOLVENT, ESPECIALLY PERCHLORETHYLENE AND TRICHLOROETHYLENE. THE SLIGHTLY SOLUBLE CHEMICAL-TREATMENT AGENT IS INTRODUCED INTO A CIRCULATING STREAM OF THE SOLVENT TOGETHER WITH A FILTER-AID POWDER WHICH IS COLLECTED TOGETHER WITH PARTICLES OF THE AGENT UPON A POROUS WALL BEFORE THE LIQUID REACHED THE TEXTILE GOODS. AS THE CHEMICAL AGENT IS DEPLETED FROM THE LIQUID CONTACTING THE GOODS, ITS RECYCLING THROUGH THE LAYER OF TREATMENT AGENT ADSORBED UPON THE FILTER POWDER RELEASE ADDITIONAL TREATMENT AGENT TO THE SOLVENT BY DISSOLVING THEREIN. CON-   SEQUENTLY, UNDISSOLVED PARTICLES OF THE TREATMENT AGENT CANNOT ACCUMULATE ON THE FIBER OF OTHER TEXTILE GOODS TO CAUSE BLOTCHING OR IRREGULAR TREATMENT.

J. H. SIEBER Oct. 31, 1972 PRQCESSI FOR THE CHEMICAL TREATMENT OF TEXTILE GOODS Filed April 28. 1969 Johannes Helm uf Sieber INVENTOR.

Attorney United States Iatent O 3,701,625 PROCESS FOR THE CHEMICAL TREATMENT OF TEXTILE GOODS Johannes Helmut Sieber, Aystetten, Germany, assignor to Bowe, Bohler & Weber KG Maschinenfabrik, Augsburg, Germany Filed Apr. 28, 1969, Ser. No. 819,893 Claims priority, application Austria, Apr. 26, 1968,

A 4,085/ 68 Int. Cl. C09b 67/ D06p 1/68; D061 1/04 US. Cl. 8-94 4 Claims ABSTRACT OF THE DISCLOSURE A process for the chemical treatment of textile goods, e.g. the dyeing, dressing or finishing of textile fibers, yarn, thread or fabric, wherein the chemical-treatment agent is slightly soluble in an organic solvent, especially perchlorethylene and trichloroethylene. The slightly soluble chemical-treatment agent is introduced into a circulating stream of the solvent together with a filter-aid powder which is collected together with particles of the agent upon a porous wall before the liquid reaches the textile goods. As

the chemical agent is depleted from the liquid contacting the goods, its recycling through the layer of treatment agent adsorbed upon the filter powder releases additional treatment agent to the solvent by dissolving therein. Consequently, undissolved particles of the treatment agent cannot accumulate on the fiber of other textile goods to cause blotching or irregular treatment.

FIELD OF THE INVENTION My present invention relates to a process for the chemical treatment of textile goods and, more particularly, to a process for the treatment of fibers, yarn, thread, fabric and the like with dressing or finishing agents and to systems for dyeing such goods.

BACKGROUND OF THE INVENTION The batch treatment of textile fibers, fabric and yarn with dyestulf or other chemical-treatment agents ranks with padding, dipping and other chemical treatment for the dyeing and dressing of textile goods in preparing them for eventual use. It is, in fact, a common procedure to dye and dress textile goods ranging from the untwisted fiber or sliver and roving to threads, yarn and fabric, with chemical solutions (e.g. of dyestuffs or dressing agents). When such solutions are employed, they have customarily been of a water base.

Recently, it has been proposed to substitute solvent dyeing and chemical treatment for treatments using waterbased systems. The use of drycleaning solvents, especially perchlorethylene and trichloroethylene has been particularly valuable, inasmuch as these solvents do not harm the fabric or detrimentally influence its hand or the hand of the fiber or yarn. Moreover, these solvents permit treatment at ordinary room temperature or a temperature close to ambient.

Consequently, solvent-chemical treatment of fiber, yarn thread, fabric and like textile goods has played an increasingly important role in textile-treatment processes. The

ice

term solvent treatment as used herein is intended to refer to the processing of the textile goods in a medium consisting predominantly of an organic solvent of the drycleaning type, usually perchlorethylene or trichloroethylene, which may be employed alone or may serve as the predominant component of a water-in-oil dispersion in which the treating agent is at least in part incorporated in emulsified water. In a further application of this principle, the water is suspended in the solvent without the aid of a chemical emulsifier and solely by mechanical action, the solvent and Water being present in a weight ratio of 2:1 to 50:1. The solvent treatment, insofar as the present application is concerned, may be a dyeing or other finishing or process treatment for such textile goods using a chemical-treatment agent which is slightly soluble in the liquid vehicle consisting predominantly of the organic solvent.

It has been found that chemical treatments of textile goods in accordance with earlier systems have had disadvantages, especially when intensive treatment was desired, for the most part as a result of the low solubility of the chemical-treatment agent at room temperature. In practice, insoluble particles of the dyestulf, usually in liquid or solid form were carried by the medium onto the fabric at which it agglomerated and to which it adhered to yield blotchy or sporadic dyeing or chemical treatment. It was not possible simply to avoid adding the dyestuff or other chemical-treatment agent in such quantities as to leave an undesired residue in the medium since the solubility of the agent was small and control of the transfer to the fabric was diflicult. It has, therefore, been the practice to introduce excess dyestufl into the medium and during the agitation, circulation and mechanical treatment of the textile goods to minimize the irregular results mentioned earlier.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide an improved process for the treatment of textile goods with chemical agents, e.g. dyestuffs or "dressing agents, in a solvent-treatment system wherein the aforementioned disadvantages are obviated.

Another object of this invention is the provision of a process for the dyeing and dressing of textile goods, e.g. yarn, fiber, thread and fabric, using a chemical-treatment agent or dyestuff which is slightly soluble in the liquid vehicle and yet which can be carried out without accumulation of insoluble treatment agent upon the textile goods.

Still further, it is an object of the present invention to provide a process for the solvent treatment of textile goods with chemical-treatment agent, especially dyestuffs which yields a more uniform result than has been obtainable heretofore.

It is also an object of the instant invention to provide an improved process for the dyeing and dressing of textile goods with treatment agents which are slightly soluble in perchlorethylene and trichloroethylene which allows convenient control and regulation of the quantities of.

chemical-treatment agent delivered to the textile goods and equally convenient control of the course of treatment.

More specifically, it is an object of this invention to provide a process for the treatment of textile goods with a chemical-treatment agent in an organic medium in which it is only slightly soluble, which admits of better control of the treatment process, prevents blotching and irregular treatment, and permits ready observation and regulation of the quantities of treatment agent delivered to the textile goods.

Still another object of my present invention is to provide an improved process for the dyeing of textile fibers, yarns, threads and fabric.

SUMMARY OF THE INVENTION These objects and others which are attainable in accordance with the present invention are readily achieved by a system for the chemical treatment, e.g. dyeing and dressing of fibers, threads, yarns and fabric, by introducing the chemical-treatment agent into a circulating organic solvent or liquid medium in which it is only slightly soluble in an amount in excess of that which will dissolve therein at the treatment temperature, together with a filter aid in the form of a filter powder, and forming from the mixture of filter powder and insolubletreatment agent or dyestuff, a filtering layer through which the vehicle is passed prior to contacting the fabric on its circulation path.

I have discovered, quite surprisingly, that the combination of a filter powder and insoluble chemical-treatment agent forms a filter layer in situ which completely prevents insoluble chemical-treatment agent from reaching the textile goods and also serves as a reservoir of chemical-treatment agent which is released to the liquid medium to replace chemical-treatment agent taken up by the textile goods.

Thus the principle of the present invention is based upon the interaction of the filter powder and the insoluble chemical-treatment agent or dyestuff which is not only mechanically entrapped in the filter layer built up by the filter powder, but also is adsorbed thereon so as to remain in a fairly uniform distribution in the liquid vehicle, even when relatively large proportions of the insoluble treatment agent or dyestuff are present.

The filter powder introduced into the dyeing liquor appears to adsorb on the particles of the filter powder, without agglomerating at any point except the filtering layer mentioned earlier and thereby concentrates substantially all of the insoluble material at this filter layer through which the dye liquid passes to the textile goods. From the latter the dyeing liquor, partially depleted as a result of dye-pickup by the textile goods, is returned in the circulating path to the filter.

I have found, also surprisingly in the face of recognized difficulties in which earlier workers have attempted to filter the insoluble dyestuff from the dyeing liquor using porous plates and microporous (sintered) filters, that the insolu ble dyestufls do not clog the interstices of the filter which is constituted in situ by the filter particles.

While I have no full explanation of the surprising interaction of the dyestuif or chemical-treatment agent with the filter particles, I believe it is the fact that the agent adheres to the particles before the particles constitute the filter which prevents the insoluble agent from clogging the filter layer after such formation.

As indicated earlier, the filter layer appears to function as a reservoir for the dyestufi which meters the dyestufl into the dyeing liquor to compensate for the pickup by the fabric.

A noteworthy additional characteristic of the present system is the ability of the filter layer to ensure intimate contact between the dyeing liquor and the insoluble dyestuif stored in the filter, thereby increasing the speed of the dissolution as the dyeing liquor passes through the filter layer; it appears also that the filter layer allows passage only of particles of such microscopic or submicroscopic size that they remain uniformly suspended and, upon contact with the textile goods, do not irregularly color the latter or agglomerate in the form of blotches therein.

Deposition-type filters, in which the porous body is formed in situ by particles entrained with the fluid to be filtered, have been proposed heretofore in numerous applications although not, to my knowledge, in connection with the dyeing and chemical treatment of fabric. In customary use of such filters, the filter layer serves merely to remove solid particles from the stream and thereby leaves the filtrate free from the component filtered therefrom. In such systems porous plates, sieves, screens and the like serve to collect the filter-aid particles to constitute the deposition filter.

In the above-described system according to the present invention, however, the filter particles only incidentally act as a solids-removing medium inasmuch as their primary function is to constitute a system for the controlled release of insoluble dyestuffs and chemical-treatment agent and a mixing medium for insuring intimate contact between the adsorbed insoluble matter and the liquid traversing the filter layer.

It is important, at this point, also to distinguish the present system from pattern-type dyeing in which the dye liquor is permitted to contact the fabric through a screen which also acts more or less as a filter. Here, there is no rapid circulation of the dye liquor such that the exchange between filter layer and liquid which is necessary in accordance with the present invention to restore the original level of dissolved dye or chemical treatment agent in the circulated liquor. It may be noted that conventional filters and screen-type structures of this nature are incapable of removing or trapping slightly soluble dyestuff particles with diameters of several microns as customarily the case. When the pore size of a conventional filter is reduced so as to enable the filter to trap such particles, they rapidly clog the filter and prevent the throughflow of the dyeing liquor. Any increase in the pore size to prevent clogging, permits passage of a substantial proportion of the dyestuff particles.

Surprisingly, it has been found that the system of the present invention appears to have an effect upon the nacure of the dyeing liquor prior to deposition of the filter particles at the porous plate or screen. It appears that the introduction of filter particles of kieselguhr or diatomaceous earth to the dyeing liquor with, and prior to the addition of the dyestulf thereto, maintains the treating agent in its finely divided form throughout the process and prevents agglomeration in the liquor.

When the dyeing liquor contains an excess of the chemical-treatment agent beyond that which is soluble in the 'medium, the excess appears to adsorb on the filter particles and is finally locked into the filter layer so that an agglomeration to form massive particles or collection thereof in the liquor is precluded. As has been noted, the finely divided chemical-treatment agent is available on the filter layer for rapid interaction with the medium and transfer thereto.

During passage of the medium through the filter layer, the solvent, preferably perchlorethylene or trichloroethylene, picks up as much of the chemical-treatment agent stored in the filter layer as is soluble in the solvent which has prior to recirculation become somewhat depleted by virtue of the deposition of the treatment agent (e.g. dyestuff) on the textile goods. As long as the dyestuif is removed from the solvent by adsorption to the textile goods, the solvent will continue to take up the dyestuif from the filter layer to the limit of its solubility, i.e. until saturation with the dyestuif. As noted earlier, the expression textile goods is intended here to include all types of fabric as Well as loose fiber, strands, rovings or sliver of fiber, twisted fiber in the form of thread and yarn, synthetic or natural fibers, and spun or extruded synthetic filaments, whether tightly wound or loose.

The present invention provides for the introduction of a filter powder together with the chemical-treatment agent and preferably in admixture therewith so that the association of chemical-treatment agent with the filter particles takes place prior to any agglomeration in the liquid medium.

In the circulating path, I provide a porous plate, screen or other trapping surface upon which the filter particles may accumulate to form the filter layer in which insoluble particles of the chemical-treatment agent are retained. It is preferred that the filter powder be mixed thoroughly with the chemical-treatment agent and the present invention, therefore, provides that the filter powder and treatment agent should be deposited upon the liquid-permeable surface one or more times prior to use of the liquor. In other words, the invention includes the step of alternately breaking up the filter layer by backwashing the fluid-permeable wall and re-establishing the filter layer thereon, this cycle occurring at least several times prior to use of the liquid medium or during the course of treatment of the textile goods. It has also been found to be advantageous to prevent passage of insoluble particles of the chemical treatment agent through the fluid-permeable wall prior to the formation of the mixed layer of chemical treatment agent and filter particles, by introducing it into the circulating medium, prior to the addition of the dyestuff or chemical-treatment agent, a preliminary quantity of the filter powder alone.

According to another feature of this invention, the liquor is heated prior to its passage through the filter layer, thereby increasing the solubility of the dyestutf or other chemical treatment agents in the solvent of the medium. It may be noted that the present invention is applicable to liquid mediums consisting predominantly of organic solvents of the character described, whether the solvent is free from or contains water in suspension or emulsion form.

According to another aspect of this invention, an apparatus for carrying out the aforedescribed process makes use of a treatment vessel in which the textile goods are brought into contact with the treating liquor, a pump and a deposition filter connected in series with one another and with this vessel for circulating the liquid medium through the filter before it reaches the treatment vessel. The system can also include means for introducing the filter powder and chemical treatment (e.g. dyestufi?) into the circulating system upstream of the filter in the direction of circulation of the liquid and preferably upstream of the pump whose pressure side may be connected to the filter while its intake side is connected to the treatment vessel. The pump thus acts as a homogenizer insuring thorough distribution of both the powder and the treatment agent in the solvent.

The apparatus may also include, as suggested earlier, a device for heating the liquor upstream of the filter, this means not only serving to increase the solubility of the treatment agent in the medium but also to decrease the viscosity of the latter and permit it to flow more readily through the filter. The heating of the medium also provides an accurate way of controlling the proportion of slightly soluble chemical-treatment agent which will be found in the liquid medium inasmuch as solubility increases with increasing temperature.

The treatment vessel may be any of the systems used heretofore for the dyeing or drycleaning of textile goods, including rotary and oscillatory drum machines, beamtype dyeing apparatus, winding frame machine and the like. Best results, however, have been obtained with drum-type machines.

The intake or suction side of the pump may be connected with a solvent supply tank while the output side of the filter may lead to a distillation unit allowing recovery of the solvent in a pure state and removal of the filter cake from the filter. Fresh solvent may also be added and I prefer to provide a bypass connectable across the fabric-treatment vessel so that the latter may be closed 01f while circulation is maintained through the bypass.

6 DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 shows a system for the dyeing of textile goods, according to the present invention;

FIG. 2 is a partial section through a filter unit, in accordance with this invention; and

FIG. 3 is a diagrammatic view of another apparatus for carrying out the invention.

SPECIFIC DESCRIPTION In FIG. 1, I show an apparatus for the chemical treatment of fabric and especially the dyeing of textiles which comprises a deposition-type filter 1 which is connected by a line 2 with the pressure side of a pump 6. The outlet side of the filter 1 is connected via a line 5 with the treatment vessel 9, the liquid return being effected by a line 3 to the intake side of the pump 6. A bypass 4 connects lines 3 and 5 so that a closed circulation path is established from pump 6 via line 2 through the filter 1 and return via lines 5, 4 and 3.

A pipe 11 is connected to line 4 and is provided with a valve 18 or some other closure device between this line and a hopper 12 through which filter powder, chemicaltreatment agent or dyestufi may be added upon removal of the cover 29. A valve 28 is provided in a duct 28a leading from the line 5 to the hopper 12 so that, when valve 13, and valve 14 between line 5 and the treatment vessel 9, are closed valves 18 and 28 can be opened to entrain the filter powder and treatment agent with the solvent circulating in the system 6, 2, 1, 5, 28a, 11, 3 and 6.

In line 3, I provided a needle trap 7 upstream of the pump 6 in the direction of circulation of the liquid medium (arrow A) which has a removable cover 7a through which filter powder and fabric-dressing chemicals can be introduced the circulating system. The needle trap 7 can thus be constituted for the feed device 12 so that the latter and lines 11, 28a and valves 18, 28 can be eliminated The system illustrated in FIG. 1 also comprises a freshsolvent supply tank 10 which may also serve as the reservoir receiving recovered solvent from a still, the tank 10 being connected by a valve 15 to line 5. Line 5 is also connected to the treatment vessel 9 via a pipe 8 having a valve 14 interposed therebetween, a further valve 30 being positioned between line 3 and the treatment vessel. In lines 2 and 5, I provide observation windows 31 and 32 through which the cloudiness, coloration or intensity of the circulated liquor can be viewed.

The valves 13-17, 19, 28 and 30 permit of circulating the liquor through any of several circulated paths as will be apparent hereinafter. These valves may be operated remotely or by hand and may be automaticresponse valves adapted to react to a change in a parameter of the circulating medium. A short circulating path is constituted from the pump 6 through the filter 1 and via the bypass 4 back to the pump, while a long circulating path extends from the pump 6 through the filter 1, the treatment vessel 9 and returns to the pump.

To increase the solubility of slightly soluble chemical agents in the liquid medium or solvent, prior to the introduction of the medium with entrained filter particles and chemical treatment agent into the filter 1, I provide a heating unit 20 along pipe 2 upstream of the filter 1. In addition, a heating jacket 20' is provided around the treatment vessel 9.

While the treatment vessel 9 can be of any conventional type, e.g. a foulard-type fabric printing machine,

any of a number of dyeing machines such as beam-type, jigger, reel-type or paddle-dyeing machine, I prefer to make use of a drum-type dyeing apparatus resembling a drycleaning machine as represented diagrammatically in FIG. 1. Within the vessel 9, therefore, I provide a perforated fabric-tumbling drum 21 which is rotated by a motor not shown and receives the fabric.

When the valve 15 is open in the first stage in the operation of the device of FIG. 1, pure solvent from the supply tank 10 is passed either via line 8 or line 4 to the intake side of pump 6 and is circulated thereby through the filter 1. Either valve 13 or valve 14 is open together with valve 16. To form the filter layer, a solution or suspension of the fiber-dressing agent or dyestufi is mixed with filter powder and introduced into hopper 12 and is metered into the system by opening valves 18 and 28 and closing valve 14. It will be understood that addition of these components can be made through the filter 7 which is designed to remove relatively large articles to prevent them from entering the pump 6. Operation of pump 6 circulates the liquid medium and the filter powder and dyestuff entrained therein through the filter 1 whereupon it accumulates on the deposition surfaces which are of tubular configuration as represented generally at 22 so that tubular filter lines are formed.

In FIG. 2, I have shown a typical filter built up in this manner. The tubular filter element is a perforated wall 1a whose apertures 1b are connected to the suction side of the pump 6 along the exterior of the tube 1a. A layer 23 of filter powder and nondissolved chemical-treatment agent forms along the interior wall of this tube to constitute the tubular filter element 22 whose inner surface 25 is represented in dash lines and receives the liquid .which passes therethrough in the direction of arrows B,

i.e. outwardly, in-finely divided form. The chemical-treatment agent is locked into the filter layer 23 in the form of particles 24 with practically the original particle size of about several microns without any appreciable agglomeration. The filter particles may be of the same particle size, but generally will be from 2 to 100 times larger. During passage of the liquor through the filter layer, any chemical agent depletion in the vessel 9 is replaced by dissolution of the chemical agent from the filter .layer built in situ. Once the filter layer has been built up in the filter 1, valve 13 of the bypass 4 may be closed and valve 14 opens to circulate the liquor through the treatment apparatus 9 in which the textile goods are tumbled in the drum 21. The liquor passing into the vessel 9 via line is saturated with the dyestuff and transfers the dyestuff to the fabric. The agitation of the fabric in the liquor insures contact of the latter with the textile goods and a uniform dyeing thereof. No insoluble treatment agent is present in the circulating liquor to adversely affeet the textile goods of the form of blotches thereon.

The system can of course be operated with variations from the basic procedure described above. For instance, it is possible to build the filter layer while allowing the liquid medium to pass through the treatment vessel 9, e.g. prior to the introduction of the textile goods into the latter, or to circulate the medium along the shorter path via the bypass 4. Also the filling device 12 and its valves 28 and 18 can be provided in line 3 and, when it is desired to use a conventional drycleaning machine having the usual circulating system, it is merely necessary to use the filling device 12 and its valves 18, 28 or to introduce the filter powder and the treatment agent into the coarse filter 7 customarily provided ahead of the pump 6.

For regeneration of the solvent, I provide a valve 17a leading to a still 17b from which the recovered solvent is returned to the tank 10, valves 16 and 17 being closed during this process. The filter 1 may be backwashed by introducing fluid through line 27 and valve 17 into the filter 1 while closing valve 17c and opening valve 19 adapted to drain the filter through line 26.

8 EXAMPLE kg. of polyester yarn on spool cores are dyed with a solvent system using perchlorethylene containing 3 kg. of

OELLITONRUBIN BF CHzCHaOH C Hz C H2 0 H H dyestuif together with a filter powder (e.g. about 10 kg.) in the form of commercial diatomaceous earth. The dyestutf and filter powder are introduced into the system of FIG. 1 by opening valves 18 and 28 and the liquor circulated through the filter 1. After a short time a filter layer is built up in the filter and consists of insoluble dye particles and filter powder, the liquor passing through the filter being saturated with dyestutf and free from any insoluble dye. Valves 14 and 30 are then opened and bypass valve 13 is closed together with valves 28 and 18, the yarn having previously been placed in the vessel 9. The heating device 20 is turned on and the color of the liquor observed until the desired concentration of the dyestuif in the liquor is reached. Heating jacket 21' is also activated to bring.

the treatment bath toa temperature higher than ambient. Upon completion of the dyeing process, the fabric is found to be totally free of blotches and irregularities and, after draining of the solvent and rinsing, is dried.

In FIG. 3, I have shown a somewhat simplified system for carrying out the present invention. In this system a pump 6' circulates the solvent via lines 33 and 34 through a vessel subdivided by a perforated partition 36 into a treatment chamber 38 in which the textile goods 37 are received and a filter compartment 35, 39 upstream of the treatment compartment. The compartment 35 has a door 41 through which filter powder and dyestuff can be introduced to form a mixture which, as it deposits on the perforated Wall 36, forms a filter layer of the character previously described. The mixture of filter particles and insoluble treatment agent is represented at 35.

The chamber 38 has a door 40 through which the textile goods may be introduced. A valve 44 in line 34 permits the closure of this line to allow solvent to be introduced to the system at the beginning of the operation while a valve drain 43 permits emptying thereof.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. A process for the dyeing of textile goods with a dyestulf, comprising the steps of:

prior to contacting the textile goods with a dyestuif liquor, introducing dyestuif particles into a solvent selected from the group which consists of perchloroethylene and trichloroethylene in which the dyestuff is slightly soluble at room temperature, said solvent also containing insoluble filter particles, thereby forming a dye treating liquor;

circulating said liquor along a closed transport path while intercepting said filter particles andvsaid dyestuff particles with a fluid-permeable surface interposed in said path to form on said surface a fluidpermeable filter layer of all of said filter particles with all of said dyestutf particles, which layer prevents said dyestulf particles from reaching said textile goods, said layer being traversed by said liquor as it is circulated along said path;

heating the solvent prior to passage thereof through said filter layer to increase solubilization of the dyestutf therein to a concentration that will dye said textile goods;

10 contacting said textile goods for the first time with said References Cited tdd 1' th 'dt t'l d d d" 2:; e ye lquor so at sai ex 1 e goo s are ye UNITED STATES PATENTS replenishing the concentration of the dyes uff in the 2,059,475 11/1936 Myers 8142 dye liquor by passing the heated dye liqu r th g 5 3,174,165 3/,1965 Dunn et a1. 8-458 the filter layer containing the dye. 3,231,324 1/1966 Young 8-142 2. The process defined in claim 1, furth r compri i g 3,056,644 10/1962 Radley et al. 893 the steps of alternately forming said layer and bre k 2,072,332 3/1937 Hatfield 8142 up said layer at least once in the course of circulating saldhquoralongsald path. 10 GEORGE F. LESMES, Primary Examiner 3. The process defined in claim 1, further comprising the step of initially forming a base layer of filter particles W Assistant i r on said surface by introducing into said solvent a quantity of filter particles prior to the introduction of said dye- U.S.C1. X.R. stulf particles into said solvent. 15 8-142, 158

4. The process defined in claim 1, wherein said filter particles are composed of diatomaceous earth. 

